@import url("https://fonts.googleapis.com/css2?family=Roboto:wght@300;400;500;700&display=swap");
* {
    font-family: "Roboto", sans-serif;
    font-weight: 400;
    margin: 0;
    padding: 0;
    font-size: 14px;
    box-sizing: border-box;
    position: relative;
    color: #000;
}
html {
    width: 100vw;
    height: 100vh;
}
body {
    background: #fff;
    width: 100%;
    height: 100%;
}
.container {
    width: 100%;
    height: 100%;
}
.flex {
    display: flex;
    justify-content: center;
    align-items: center;
}
img {
    width: 100%;
}
.a1, .b1 {
    position: fixed;
    z-index: 999;
    top: 0;
    left: 0;
}
.a2, .b2 {
    position: fixed;
    z-index: 999;
    bottom: 0;
    left: 0;
}
.a3, .b3 {
    position: fixed;
    z-index: 999;
    top: 0;
    left: 0;
}